Heretofore, as a process for producing a 9,10-dialkoxyanthracene, a process is, for example, known wherein an anthracenedione compound is reduced and alkylated as disclosed in U. Seitz et al., Synthesis, 686-688 (1986). The process disclosed in this publication is a process wherein in a two phase solvent system having water and methylene chloride mixed, hydrosulfite is used as a reducing agent, and methyl iodide is used as an alkylating agent. However, the process disclosed in this publication has a problem of environmental pollution by methylene chloride, and further it can hardly be regarded as an industrially advantageous process, as an expensive alkylating agent is employed.
Further, JP-A-2000-119208 discloses a process wherein an anthracenedione compound is reduced and alkylated in an alcohol medium by using hydrosulfite as a reducing agent and diethyl acetate as an alkylating agent. However, according to the test conducted by the present inventors, if dipropyl sulfate or propyl bromide was used as an alkylating agent when dipropoxy anthracene was prepared by the process disclosed in this publication, by-products were substantial, and the desired dipropoxyanthracene was not obtained. Further, in a case where butyl bromide was used as an alkylating agent, dibutoxyanthracene could not be obtained.
Under such a circumstance, the present inventors have conducted an extensive study for the purpose of providing a process for producing, industrially advantageously in good yield, a dialkoxyanthracene, particularly a high purity anthracene diether such as 9,10-dipropoxyanthracene or 9,10-dibutoxyanthracene, and as a result, the present invention has been accomplished.